1. Field of the Invention
The present invention relates to a buffer member, and an impact absorbing device of a hard disk drive apt to be affected by an impact. More particularly, the present invention relates to a buffer member for protecting a hard disk drive against the impact occurring when a mobile information apparatus mounted with the hard disk drive falls, an impact absorbing device formed of the buffer member, and a mobile information apparatus having a built-in impact absorbing device storing a hard disk drive.
2. Background Art
A hard disk drive (hereinafter referred to as “HDD”) moves a magnetic head in a head load state, and records or reproduces data at a target record position. In the head load state, the magnetic head keeps a predetermined distance (float spacing amount) from the surface of a disk rotating at a high speed. The float spacing amount between the magnetic head and the disk surface has decreased from year to year in order to increase the recording density of the HDD.
When the impact force is applied especially in the direction perpendicular to the disk surface during operation of the HDD, a phenomenon called head slap where the magnetic head displaces by the float spacing amount or longer to hit the disk surface is apt to occur. The head slap causes physical damage of the recording surface of the disk or the head. This damage disables recording or reproducing of data on at least the damaged part of the disk, and disables use of the whole recoding surface of the disk and breaks the HDD at worst.
When the HDD is mounted on a stationary information apparatus such as a desktop computer, an impact force as strong as the head slap is caused is hardly applied to the HDD. While, an HDD mounted on a mobile information apparatus such as a notebook personal computer (hereinafter referred to as “notebook PC”) is always exposed to risk of receiving such an impact force. In other words, a user can easily carry or move a notebook PC due to its portability, but the user is accidentally apt to bump the notebook PC against a firm matter such as a corner of a desk or drop it during carrying or moving it. A notebook PC is produced to be light in weight and compact in order to secure the portability, so that such an impact force easily transfers to the built-in HDD to result in breakage of the HDD.
Therefore, a small HDD built in a notebook PC has been recently provided with a magnetic head evacuating function in order to increase the impact resistance especially during operation. In a 2.5-inch HDD, for example, in an idling state having no access demand for a certain time during either of non-operation and operation, the magnetic head is evacuated to a position separated from the disk by head unload operation. Here, in the head unload operation, the magnetic head is moved into a member for evacuation arranged at a position separated from the disk, and is locked at that position. Such an operation prevents an impact force serving perpendicularly to the recording surface of the disk from physically damaging the magnetic head or the dish surface.
In other words, when the magnetic head is not required to be positioned on the recording surface of the disk of the HDD dependently on the operation mode, the head is evacuated from the disk to prevent the head slap.
During access operation (access operation of the HDD) of the magnetic head to the disk, however, the magnetic head lies in the head load state as a matter of course. A perpendicular impact force causes the head slap to damage the disk. In other words, the possibility that an impact force perpendicular to the disk surface causes the head slap to damage the disk during access operation of the HDD is kept high. Therefore, the HDD cannot be protected against an impact caused when the user accidentally bumps the notebook PC against a firm matter or drops it during access operation of the HDD. A weak impact applied to the HDD by daily handling and repetitive vibration of high frequency damages the HDD or disk surface. Here, an example of the daily handling is putting the notebook PC on a desk or carrying the notebook PC with a bag. A conventional buffer member used in an electronic apparatus such as a HDD and a mounting structure to the electronic apparatus are described hereinafter with reference to the drawings.
FIG. 14 is a schematic perspective view of a built-in electronic apparatus via a conventional buffer member. When an impact such as drop is applied to electronic apparatus 10, buffer member 31 mounted to each of four corners of electronic apparatus 10 reduces the impact force applied to the electronic apparatus 10 body.
A buffer member formed by combining a plurality of materials of a different impact buffering characteristic is proposed.
FIG. 15 is a schematic front view showing an example where a buffer member that is formed of a plurality of members and absorbs vibration and impact is disposed between electronic apparatus 10 and a storage part (not shown) of electronic apparatus 10.
In FIG. 15, the buffer member is formed of first buffer member 41 of high compressive elasticity modulus and second buffer member 42 of low compressive elasticity modulus. The buffer member has a two-stage structure as below. When a weak impact is applied to electronic apparatus 10, only soft second buffer member 42 softly absorbs the impact. When a strong impact is further applied to electronic apparatus 10, the impact that cannot be completely absorbed by soft second buffer member 42 is absorbed by newly added hard first buffer member 41. Therefore, each of the first and second buffer members absorbs the impact by each elastic deformation. This structure can reduce various impacts, namely from a weak impact to a strong impact, more effectively than a single buffer member.
An example of the conventional art document information related to this technology is Japanese Patent Unexamined Publication No. H11-242881.
As long as the impact is absorbed simply by elastic deformation, however, it is considered to be difficult that the buffer member and impact buffering method of FIG. 15 effectively reduce the impact force to prevent the electronic apparatus body from being fatally damaged.
FIG. 16 is a schematic front view showing an example of a conventional buffer member that is formed of a complex member having sheet-like second buffer material 52 in first buffer material 51 and is unitarily molded.
When an impact is applied to electronic apparatus 10, this buffer member absorbs the impact by bending of buffer material 52 and then absorbs the impact by buckling of a bending part. Therefore, the buffer member can receive impact compressive force for a relatively long time, and can sufficiently exhibit the buffer performance.
An example of the conventional art document information related to this technology is Japanese Patent Unexamined Publication No. 2004-315087.
In the buffer member and impact buffering method of FIG. 16, however, sheet-like second buffer material 52 does not bend and does not exhibit the buffer effect when the impact is weak. Electronic apparatus 10 propagates generated high-frequency vibration to the product case that stores electronic apparatus 10 via sheet-like second buffer material 52. When a notebook PC is used, the vibration of the hard disk device is propagated to the case side, namely to the case part of the notebook PC touched by the user. This is a problem about the product quality.
FIG. 17 is a schematic perspective view showing a conventional example of combination of buffer materials in a packing material.
In this example, also, a plurality of buffer materials are unitarily molded and buckling material 62 buried in buffer material 61 is buckled, thereby improving the buffer performance. Buckling material 62 is molded unitarily with buffer material 61. Buckling material 62 is set shorter than buffer material 61 in the thickness direction to prevent a packed object from being damaged.
An example of the conventional art document information related to this technology is Japanese Patent Unexamined Publication No. H02-205579.
However, also in the example of FIG. 17, the unitary molding of the buffer material and buckling material causes the impact to be propagated through the buckling material similarly to the example of FIG. 16.